Session 3. Impacts of altered regimes of extreme abiotic events
Summary report
Participants considered a number of recent changes in forest ecosystems and discussed whether they could be
attributed to climate change. They considered the following evidence in particular.
 Temperate
and boreal forests subject to increasing temperatures (less snow and permafrost) and greater
incidence of extreme weather events (droughts, increased precipitation/floods, higher temperatures, high
winds, snow storms) that impact forests by greater incidence and impact of fires, windfall and landslides,
that cause changes in species composition and associations in forests that can cause predisposition to other
biotic events (insects, diseases and other pests).
 The
impacts of climate change on forests will differ by forest type and region. The tropical dry forest
ecosystem in southern India, discussed in the session, showed that they are impacted by droughts and high
temperatures which can cause delayed mortality depending upon the species, diameter classes, severity of
the extreme weather event and other pests. In the African savannah ecosystem in Cote d’Ivoire, earlier dry
seasons are bringing about changes in fire use resulting in less intense fires which in turn results in a shift
from grasslands to wooded lands. In Mongolia there has been a 4 million ha loss of forests during the last
century, caused by a combination of climate change, extreme weather events, fire, insects and diseases and
unsustainable land-use practices, including animal grazing, illegal logging and illegal migration. Historical
indicators showed an increase in forest fires following years of decreased precipitation. Indicators of a
decrease in the incidence of forest fires were correlated with a 16th century Mongolian King’s decision to
manage a forested area. In Korea, the very young nature of the forests makes it difficult to separate effects
of climate change from changes associated with natural succession. In central Europe, there are now more
dead trees (mostly caused by drought) than at the peak of the period associated with «Waldsterben» (forest
decline).
 Decline
in mangroves which is possibly related to the changes in the salinity of the water could be due to a
decrease in the in flow of fresh water by decreased precipitation or the increase in the addition of salt water
caused by an increase in the number of hurricanes. Correlation is not easy to determine.
 Effects of
a combination of extreme weather conditions and possible changes in climatic trends are
complexly linked (i.e. increased wind with or without increased temperatures)
 There
is a complex link between abiotic and biotic events but they are difficult to disassociate.
Session participants noted the following when discussing the possible future impacts of climate change on
forests.
 Correlating
longer term climate change and the incidence and impact of extreme weather events on fire,
windfall, floods, landslides etc. that impact forests and forest management, are difficult to predict
 Increased
frequency of events like hurricanes may decrease the resilience of forests to recover and may in
fact have impacts on regenerative species and the distribution of biomass.
 Climatic changes may
expose some ecosystems to new risks that they are not well adapted for.
 The
diversity of both the species in a forest and the management practices used to manage the forest will all
have varying effects on the forest thus making it harder to predict future outcomes.
 Some
of these changes might have an affect on the operational aspects of harvesting, such as less frost
decreasing access to forested areas and not enabling equipment to be moved.
The future impacts of climate change on people and institutions were discussed and the following points were
noted.
 The
majority of speakers highlighted the greater incidence and impact of fires and the resulting change in
seasons that these fires create in forest, savannah and grassland ecosystems exacerbated by extreme weather
events (drought, higher temperatures and wind) that impact the lives and livelihoods of communities.
 The
relationships between people, forests and climate change are very complex and the impacts on people
and institutions are difficult to model or predict in future scenarios, but in a Central American study there is
anticipated to be less high fire risk areas and more moderate fires risk areas (this includes climate and socioeconomic and behavioural changes).
 There
was insufficient past research in assessing climate change and extreme weather events to predict
future impacts on people and institutions with confidence.
 The
human adaptation to changing seasons is that fires are being used by different land-users at different
seasons for different reasons, with a change in advocacy of burns.
 The
point was made that greater variation in weather events is expected. Coping with this will increase the
costs of forest management, and traditional means of costing forestry projects may become inappropriate.
 Questions were
asked about the reality of predicting the future impacts and how much would be attributed
to climate change.
In considering adaptation measures, participants noted the forest management risk assessment needs to
recognize instances where: response options are not necessary; management response to the risk is
worthwhile; and a management response option is not possible. There may be a need to explore more diverse
harvesting regimes including selective logging and encourage breeders to select for other factors than fast
growth. Participants also suggested that forest managers not plant monocultures.
Session participants noted that more investment in forest research in developing countries is needed as many
adaptation options are hindered by a lack of knowledge. It was noted that it must be recognized that polices
must vary for different conditions, such as natural forests vs. planted and managed forests. It was also noted
that local peoples must be involved in any policy-making process as they will be the ones ultimately impacted
by such policies. Global policies may be needed to support the forests of the world particularly in developing
countries where resources are more difficult to obtain.